| ( | 600 | + | x | ) | ÷ | 18 | = | ( | 480 | + | x | ) | ÷ | 15 |
| 方程左边 = | 600 | × | 1 18 | + | x | × | 1 18 |
| = | 100 3 | + | x | × | 1 18 |
100 3 | + | 1 18 | x | = | ( | 480 | + | x | ) | ÷ | 15 |
| 方程右边 = | 480 | × | 1 15 | + | x | × | 1 15 |
| = | 32 | + | x | × | 1 15 |
100 3 | + | 1 18 | x | = | 32 | + | 1 15 | x |
1 18 | x | − | 1 15 | x | = | 32 | − | 100 3 |
| - | 1 90 | x | = | 32 | − | 100 3 |
| - | 1 90 | x | = | - | 4 3 |
4 3 | = | 1 90 | x |
1 90 | x | = | 4 3 |
| x | = | 4 3 | ÷ | 1 90 |
| = | 4 3 | × | 90 |
| = | 4 | × | 30 |
| x | = | 120 |